1. Field of the Invention
The present invention relates to a new coloring compound, a yellow toner including the coloring compound, a sheet for heat-sensitive transfer recording having a coloring material layer including the coloring compound, and an ink including the coloring compound.
2. Description of the Related Art
With a change in lifestyle due to recent scientific and technological advances, dyes have become used not only in the conventional applications such as dyeing or coloring various materials including fibers, plastics and leathers, but also in a variety of industrial fields, taking advantage of their characteristics of recording or displaying information. Particularly, as personal computers have rapidly come into wide use in recent years, hard copy technologies typified by electrophotographic recording and heat-sensitive transfer recording have been advanced for recording the character and image information output therefrom.
The electrophotographic recording method generally involves: forming an electrical latent image of static charge on a photosensitive member including a photoconductive material by various means; developing the latent image with toner to make a powder image; transferring, as needed, the powder image to paper or the like; and then fixing the image by heating, pressurization, solvent vapor, or the like. In recent years, a method for obtaining a full color image has also been put to practical use, which involves performing exposure and latent image formation using dispersed light and developing the latent image with color toner. In addition, a digital full color copier or printer in which the electrophotographic process is digitized has gone into actual use, which has made it possible to achieve images excellent not only in resolution and gradation property but also in color reproducibility without irregular color. As a result, there is a need for development of colorants for toner good in color tone and excellent in light resistance.
With recent widespread use of digital cameras, home printing of photos has now come to prevail; printers using a heat-sensitive transfer recording system are now in increasing demand, which have advantages in that the image recorders thereof can be made small-sized and low-cost, operation and maintenance are easy, and running costs are low. The heat-sensitive transfer recording method involves superposing a heat-sensitive transfer recording sheet having a coloring material layer including a heat-transferable colorant on a sheet-like substrate and an image-receiving sheet having a dye-receiving layer on the surface and heating the heat-sensitive transfer recording sheet to transfer the colorant in the coloring material layer of the heat-sensitive transfer recording sheet to the image-receiving sheet for recording. In the heat-sensitive transfer recording method, the heat-sensitive transfer recording sheet and the colorant contained in the ink composition used in the heat-sensitive transfer recording sheet are very important because they have a large influence on the speed of transfer recording, the image quality and storage stability of recorded matter, and the like. Performances specifically required for the colorant used include spectral properties capable of realizing a preferable color reproduction range, compatibility between heat transferability and fixability after transfer, thermal stability, and various fastness properties of the resulting image.
Pyridone azo dyes and pigments are known as coloring compounds used as yellow colorants (for example, see patent documents 1 to 3). These pyridone azo dyes generally have large molar absorption coefficients, and the toners and heat-sensitive transfer recording sheets obtained using these coloring compounds as colorants have high coloring ability, clarity and coloring power.
Pigments such as C.I. Pigment Yellow 93 and C.I. Pigment Yellow 155 have conventionally been commonly used as yellow colorants for toner, but there has been a need for a further improvement in a color tone and compatibility with resin. To improve these characteristics, new pyridone azo dyes for toner have been studied. For example, patent documents 4 to 7 propose the use of oil-soluble pyridone azo dyes as yellow toner colorants for electrophotography. However, a further improvement has been desired for satisfying characteristics as a toner colorant, particularly all of the color tone, compatibility with resin and light resistance, at a high level.
Methine disperse dyes such as C.I. Disperse Yellow 201 or disazo disperse dyes such as C.I. Disperse Orange 13 has previously been used as yellow colorants employed for heat-sensitive transfer recording sheets. However, to further improve characteristics such as, particularly, a color tone, ink-forming properties (solvent solubility) and light resistance, new yellow colorants used for heat-sensitive transfer recording sheets are being studied. For example, patent documents 8 to 13 propose the use of pyridone azo coloring compounds as yellow colorants. Nevertheless, a further improvement has been desired for satisfying all of the above characteristics as a colorant for heat-sensitive transfer recording sheets at a high level.
Patent document 1: Japanese Patent Application Laid-Open No. H09-111143    Patent document 2: German Patent No. 2004487    Patent document 3: U.K. Patent No. 2032448    Patent document 4: Japanese Patent Application Laid-Open No. H03-042676    Patent document 5: Japanese Patent Application Laid-Open No. H06-059510    Patent document 6: Japanese Patent Application Laid-Open No. H08-110653    Patent document 7: U.S. Pat. No. 4,734,349    Patent document 8: U.S. Pat. No. 4,968,657    Patent document 9: Japanese Patent Application Laid-Open No. H05-255602    Patent document 10: Japanese Patent Application Laid-Open No. H05-331382    Patent document 11: Japanese Patent Application Laid-Open No. H11-314467    Patent document 12: Japanese Patent Application Laid-Open No. 2000-062327    Patent document 13: Japanese Patent Application Laid-Open No. 2000-239549